There are two vinegar production processes, including solid-state fermentation and liquid-state fermentation, of which the solid-state fermentation has been widely applied due to pure taste of vinegar products and simple process. The solid-state fermentation is characterized in that the materials (brewing mass) are in solid state during the acetic fermentation, and alcohol is oxidized to acetic acid and other flavor substances by acetic bacteria and other microorganisms in the brewing mass during the fermentation. The reproduction and fermentation of acetic bacteria propose high requirements on temperature, acidity, oxygen content and etc. in the growth environment. Therefore, the acetic bacteria often realize reproduction in a part of the brewing mass with appropriate growth environment and are active in fermentation to result in the rising of temperature of the brewing mass. To make the entire brewing mass fermented uniformly and to keep the temperature of the brewing mass within an appropriate range, the brewing mass needs to be overturned.
Acetic fermentation in conventional solid-state fermentation vinegar production processes is carried out in unit of vinegar jars. Overturning the brewing mass (also known as “jar overturn”) is mostly manual and empirical, with high labor intensity and poor working conditions. In the 1990s, the solid-state fermentation vinegar production processes were improved to replace vinegar jars with vinegar pools (“replacement of jars with pools”) and replace manual brewing mass overturn with brewing mass overturn machines. The existing brewing mass overturn machines have a common structure that a hopper moves into a brewing mass pool to fill itself with the brewing mass under the drive of a transmission chain and then lifts up as it moves along with the chain, and the hopper makes its mouth face downward when it moves to the other side so that the brewing mass in the hopper falls back to the brewing mass pool due to gravity. The mechanical brewing mass overturn process is thus realized. The following relevant published patent documents have been already known: Patent No. ZL94226760.5, titled “Brewing Mass Overturn Machine”; Patent No. ZL02216018.3, titled “Brewing Mass Overturn Machine”; Patent No. ZL200520076229.X, titled “Light Brewing Mass Overturn Machine”; and, Patent No. ZL200520076230.2, titled “Brewing Mass Overturn and Discharging Machine”. For such brewing mass overturn machines, although the replacement of manual brewing mass overturn with mechanical brewing mass overturn greatly decreases the labor intensity and improves the production efficiency, such brewing mass overturn machines are still reliant on manual operation and control, i.e., time, frequency, depth and other conditions of brewing mass overturn are determined upon what the workers see and what they smell in combination with their subjective experience. This lacks scientific support. Although the temperature, acidity, smell, color and other parameters of the brewing mass may be detected by physical and chemical analysis during the fermentation of the brewing mass to determine whether or not a brewing mass overturn operation is needed, it is always costly and laborious; furthermore, the detection points are too limited to realize overall monitoring.